1. Field of the Invention
The present invention relates to a testing method for evaluating processability (extrudability) of a viscoelastic material (elastomer) including rubber, resin and the like.
More specifically, the present invention relates to:                a method and a device for evaluating the processability of the viscoelastic material,        a method for setting a condition for processing the viscoelastic material, and a device for processing the viscoelastic material; and        a method for controlling the processing operation of the viscoelastic material.        
2. Description of the Related Art
A viscoelastic material such as a rubber product has quality, performance and processability which are highly sensitive to characteristics (especially, plasticity, viscosity, elasticity and the like) of its blended rubber (unvulcanized). Therefore, production, evaluation, research and development of rubber composition are in need of obtaining accurate and precise information about processability of the material (blended rubber) by measuring characteristics of the material (blended rubber).
At a mixing step for mixing the rubber in production, dispersion in the material may greatly affect processability at the next extrusion step. For reducing defect rate in processing operation, controlling the material with higher accuracy and precision is demanded recently.
Described below include measures for predicting the processability (extrudability), which measures are to be accurately and precisely evaluated:
[1] Evaluation of dispersion in extruded cross sectional shape (in other words, predicting dispersion rate of material discharge).
[2] Prediction of screw speed of extruder (in other words, predicting average material discharge).
[3] Judgment of extrudability of the material (in other words, judging whether or not the screw speed is enough for adjusting external view and cross sectional shape of extruded product).
In general, a device for measuring viscoelasticity (an important factor for rubber processing) includes what is called a Mooney viscosimeter which was released in 1934 by M. Mooney and has been widely used. Measurement method with the Mooney viscosimeter is standardized by JIS-K6300, where JIS stands for Japanese Industrial Standard.
Ordinarily, the Mooney viscosity is measured at 100° C. After preheating for 1 minute, a rotor is turned at 2 rpm. Then, after another 4 minutes, a torque about 84.6 kg·cm is defined as 100 points for a conventional Mooney viscosity ML1+4.
Generally, the Mooney viscosimeter is widely used. With the use of the rotor, however, Mooney viscosity is measured at one point on a time axis in a broad shear speed range, thus causing difficulty in obtaining accurate and precise rubber mixed condition.
Summarizing the above, it is unlikely to obtain with the Mooney viscosimeter accurate and precise information about extrudability (extrusion discharge, extrusion dispersion and the like) which is dependent on the rubber mixed condition.